Well this is the formula we are using .... Under perfect conditions...
with 802.11n .... 40mhz channel = MCS 15 = 270/300mbps (air rate)
connection.
20mhz channel = MCS 15 = 130mbs (air rate)
connection
10mhz channel = MCS 15 = 65mbs (air rate)
connection.
5mhz channel = MCS 15 = 32.5mbs (air rate)
connection
802.11a/b/g radios are about 40%-50% efficient in terms of air-rate to
tcp thruput conversion.
802.11n radios are about 60-75% efficient ...
so....5mhz channel with a MCS 15 air rate of 32.5mbs should translate
into = 19mbps to 24mbps tcp thruput....
in the field you want to leave yourself plenty of headroom and some
margin.... a 5hz channel would be a bit on the margin for a 10x10mbs
connection...
therefore using 10mhz channel should give you up to 30meg of bandwidth
capability on each of the cpe's....(i.e 15x15)
also:- this chart is a good reference when trying to decipher MCS rates
....
http://en.wikipedia.org/wiki/IEEE_802.11n-2009
Hope this helps.
Regards
Faisal Imtiaz
Snappy Internet& Telecom
On 8/4/2010 3:54 PM, Fred Goldstein wrote:
At 8/4/2010 03:37 PM, Jerry Richardson wrote:
It will not work.
But you would be surprised how well these run at 5 or 10 MHz channels.
With how much spacing between them? If I could put them on adjacent
10 MHz center frequencies, that would solve a lot of problems, and
even 5 MHz channels with 10 MHz spacing (and thus a 5 MHz guard band)
would be reasonable. But 20 MHz spacing is problematic.
How much throughput can a quarter-channel get? The Rocket data sheet
is not very complete; it doesn't even mention subchannel
support. The RM5 spec sheet says that MCS12 has -84 dB
sensitivity. That gets 78 Mbps in a full 20 Mbps channel, 162 in a
double-wide, and a bit more with the short guard interval. If I
could share 15 Mbps among the sector users, in 5 MHz, I think
everyone should be happy. And I'd expect -89 to -90 sensitivity.
Jerry Richardson
Sent Mobile
On Aug 4, 2010, at 12:33 PM, "Fred R. Goldstein"
<fgoldst...@ionary.com> wrote:
If I have a site with, say, Ubiquiti Rocket M5 radios plugged into
120 degree sector antennas, with Airmax (TDMA) turned on, do they
have to be on separate frequencies, or can they coexist on one? The
5.8 GHz band is kind of crowded to be having three access frequencies
plus two or more backhaul frequencies... thanks.
--
Fred Goldstein k1io fgoldstein "at" ionary.com
ionary Consulting http://www.ionary.com/
+1 617 795 2701
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